This invention relates to a detecting element utilized in an improved electrical resistance type of fluid leakage detecting apparatus for detecting external leakage of fluid from piping systems and equipments installed therein. More particularly, this invention relates to a fluid leakage detecting element for use in a fluid leakage detecting apparatus suitable for detecting a variety of modes of fluid leakage ranging from leakage in a very slight quantity such as oozing-out to leakage in a large quantity from plant equipments, pressure vessels, oil pipe lines, oil tanks, and pumps, motors and various control valves controlled by various kinds of fluids.
Generally, in a plant such as an oil plant, many fluid piping systems are closely arranged for operating the plant, and many valves and other fittings are installed in the piping systems.
Cracks tend to occur on the pipes of the piping systems and valves and other fittings installed therein on gaps tend to appear at the connections, as a result of an extended period of time of use or impartation of an external force by, for example, an earthquake. Occurrence of a crack on any one of the pipes, valves and other fittings of the piping systems or appearance of a gap at any one of the connections will result in leakage of fluid through the crack or gap, and this fluid leakage will lead to impairment of the safety of the plant. Therefore, an apparatus for detecting leakage of fluid is used to ensure the safety of the plant.
In one type of prior art fluid leakage detecting apparatus, a change in the electrical resistance value of a resistive element due to its contact with a fluid to be detected is utilized for the detection of fluid leakage, as, for example, disclosed in Japanese patent application Laid-open No. 113928/80 and Japanese patent application Laid-open No. 151250/80.
In such a resistance type fluid leakage detecting apparatus, the detection sensitivity, response characteristic, anticorrosion property, mechanical strength and reliability of the resistive element must be fully taken into consideration. However, none of the prior art detecting apparatus have been fully satisfactory in these aspects.